re: motion-independent liveness probe; n looks like craft-per-member

entities2.moving() finds entities by displacement between two samples, so
anything stationary is invisible -- the entire explanation for the +/-10 swing
that made the previous run's count useless. liveness_probe.py enumerates by
definition pointer over the entity heap instead, moving or not, and reads hull
as f32 at position+0x154. The series is monotone rather than oscillating:
298 -> 280 over 164 s, with the decline matching the 18 disappearance events
exactly.

The hunting pilot does kill: one hull crossing caught directly, an
e010_ADAN_Attacker_S at t=57 s. The previous run's worry that SYLPH_HUNT shoots
but never destroys anything is settled.

Recorded as a non-result so the next run does not misread it: zero births in
164 s does NOT favour either wave model. The roster finding already established
that every participant is allocated at mission load, so neither a clock nor an
event model would produce an allocation. An arrival must be a state change on an
existing entity.

The mystery member field n now has a candidate meaning: the number of craft a
roster member spawns. Static sum(n) for turrets is 216 against 214 sites found,
with the count already falling before the first sample, where Count alone
predicts 21 -- off by an order of magnitude.

Not promoted, and the reason is a confound in my own measurement rather than the
data: the probe counts definition-pointer SITES, not entities. The player is one
member and yields two sites, and DeltaSaber_T yields exactly double its sum(n),
so some entity types hold several pointers to their definition. Until sites are
collapsed into distinct entities the turret match could be a coincidence between
a x1 multiplicity and a x1 ratio. The capital-ship rows undershoot for a
separate and expected reason: phases 2 and 3 have not started.

tools/re-capture/liveness_probe.py

@@ -0,0 +1,82 @@
+#!/usr/bin/env python3
+"""A STABLE live-entity roster with hull, so kills and arrivals are observable.
+
+Why not reuse the pilot's scan: entities2.moving() finds entities *by motion*
+between two samples, so anything stationary in the window is invisible. That is
+why the pilot's count swings +/-10 between ticks and why no wave conclusion
+could be drawn from it (mission-wave-arrivals.md).
+
+This enumerates by definition pointer instead: every aligned word in the entity
+heap that equals a known unit-definition VA marks an entity, whether it is
+moving or not. Hull is f32 at position + 0x154 (HULL_OFF, already confirmed in
+pilot.py), so a death is a hull crossing to <= 0 and an arrival is a position
+that was not there before.
+"""
+import os, sys, time, struct, collections
+sys.path.insert(0, __file__.rsplit('/', 1)[0])
+import gmem, gworld, entities2
+
+ENT_LO, ENT_HI = entities2.ENT_VA_LO, entities2.ENT_VA_HI
+HULL_OFF = 0x154
+
+def enumerate_entities(fd, defs, delta):
+    """All entities in the heap region, moving or not."""
+    lo, hi = gmem.va_to_off(ENT_LO), gmem.va_to_off(ENT_HI)
+    out = []
+    pos = lo
+    while pos < hi:
+        n = min(1 << 24, hi - pos)
+        blob = os.pread(fd, n, pos)
+        for k in range(0, len(blob) - 3, 4):
+            nm = defs.get(blob[k:k+4])
+            if nm:
+                out.append((pos + k - delta, nm))
+        pos += n
+    return out
+
+def hull(fd, off):
+    try:
+        return struct.unpack('>f', os.pread(fd, 4, off + HULL_OFF))[0]
+    except Exception:
+        return None
+
+def main():
+    secs  = int(sys.argv[1]) if len(sys.argv) > 1 else 180
+    every = int(sys.argv[2]) if len(sys.argv) > 2 else 10
+    delta = int(sys.argv[3], 0) if len(sys.argv) > 3 else 0x130
+    w = gworld.World(); fd = w.fd
+    defs = entities2.definitions(w)
+    print('unit definitions: %d' % len(defs))
+    if not defs:
+        print('NO DEFINITIONS -- not in a mission'); return 2
+
+    ents = enumerate_entities(fd, defs, delta)
+    print('entities enumerated (motion-independent): %d' % len(ents))
+    print('composition:', collections.Counter(n for _, n in ents).most_common(8))
+
+    log = open('/tmp/liveness.tsv', 'w'); log.write('t\talive\tborn\tdied\n')
+    prev = {off: hull(fd, off) for off, _ in ents}
+    names = dict(ents)
+    t0 = time.time()
+    while time.time() - t0 < secs:
+        time.sleep(every)
+        el = round(time.time() - t0)
+        cur_ents = enumerate_entities(fd, defs, delta)
+        cur = {off: hull(fd, off) for off, _ in cur_ents}
+        for off, n in cur_ents: names.setdefault(off, n)
+        born = [o for o in cur if o not in prev]
+        gone = [o for o in prev if o not in cur]
+        died = [o for o in cur
+                if prev.get(o) is not None and cur[o] is not None
+                and prev[o] > 0 >= cur[o]]
+        alive = sum(1 for o, h in cur.items() if h is not None and h > 0)
+        print('  t=%4ds  entities=%3d alive=%3d  born=%2d died=%2d gone=%2d  %s'
+              % (el, len(cur), alive, len(born), len(died), len(gone),
+                 [names[o].replace('UN_', '') for o in (born + died)[:4]]), flush=True)
+        log.write('%d\t%d\t%d\t%d\n' % (el, alive, len(born), len(died))); log.flush()
+        prev = cur
+    log.close()
+    return 0
+
+if __name__ == '__main__':
+    sys.exit(main())

tools/re-capture/liveness_session.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+set -u
+export HOME=/sylph-home/re SDL_AUDIODRIVER=dummy DISPLAY=:98
+export PYTHONPATH=/sylph-home/.local/lib/python3.12/site-packages
+SD="$(cd "$(dirname "$0")" && pwd)"
+SECS="${1:-180}"; EVERY="${2:-10}"; HUNT="${3:-1}"
+CFG=/tmp/nav-live.json
+"$SD/launch_mission.sh" fly || { echo "BOOT FAILED"; exit 1; }
+if python3 "$SD/entities2.py" self 0x130 "$CFG" >/dev/null 2>&1; then
+  SYLPH_HUNT="$HUNT" SYLPH_KILL_TURRETS=1 nohup python3 "$SD/pilot.py" "$CFG" "$SECS" \
+      </dev/null >/tmp/live-pilot.log 2>&1 &
+  PILOT=$!; echo "--- pilot (SYLPH_HUNT=$HUNT)"
+else PILOT=""; echo "--- BIND FAILED, no pilot"; fi
+python3 "$SD/liveness_probe.py" "$SECS" "$EVERY"; rc=$?
+[ -n "$PILOT" ] && kill "$PILOT" 2>/dev/null
+echo "LIVENESS DONE rc=$rc"